Alcohol abuse is a national problem that extends into virtually all aspects of society. Over 17,000 people are killed each year in alcohol related traffic accidents due to the detrimental effects of alcohol on motor control and judgment. Given the magnitude of the driving under the influence (DUI) problem, increased attention is being focused on interlocks as a tool to prevent intoxicated individuals from operating motor vehicles and machinery.
The use of alcohol measurement devices to prevent drunk driving has been proposed. Although reflex and response testing methods have been disclosed (see U.S. Pat. No. 5,224,566), the vast majority of disclosed methods involve the use of a breath device to detect either the alcohol in the lungs of the prospective operator or the alcohol present in the air within the passenger compartment (see U.S. Pat. No. 4,592,443, U.S. Pat. No. 5,055,268, U.S. Pat. No. 5,426,415, and US 2004141171A1). In the event of alcohol detection (or detection of alcohol above a threshold), operation of the vehicle is typically prevented via restriction of the ignition system. However, many of the breath-based interlocks are limited in their effectiveness due to numerous methods for circumventing or defeating the test. Principal among these is the absence of inherent proof that the prospective driver is the individual providing the breath sample for the alcohol test, thus potentially allowing individuals other than the driver to provide the breath sample or the driver using an artificial breath sample (e.g. air in a balloon) for the interlock measurement.
In order to address these limitations, several combinations of breath and biometric devices have been disclosed in the art. The most common biometric methods in interlocks are voice recognition (see U.S. Pat. No. 4,738,333 and U.S. Pat. No. 6,748,301), video recognition (see U.S. Pat. No. 6,748,792 and U.S. Pat. No. 6,956,484), and bodily feature identification (see U.S. Pat. No. 4,996,161). In all of these cases, the biometric device relies upon a measurement or action that is distinct from the breath alcohol measurement. Consequently, there is concern over the robustness of the combined measurement methods as well as the potential for the measurement to be defeated by taking advantage of the two distinct measurements. For example, in some situations the potential exists for the biometric measurement to be acquired from one potentially intoxicated individual while the alcohol measurement is acquired from a second, sober individual.
Recently, transdermal alcohol sensors have been disclosed as an alternative to breath and blood alcohol measurements. US 2005230175 A1 discloses the use of a transdermal alcohol sensor as part of an ignition interlock to prevent drunk driving. However, transdermal alcohol measurements require contact between the sensor and skin over long periods of time to measure the alcohol present in perspiration as it leaves the body. The long measurement time represents a significant drawback of transdermal measurements for interlock applications. Furthermore, the transdermal method has no inherent means for subject identification other than the physical attachment of the sensor to a body part. Thus, there is no integral means to ensure that the driver is the person wearing the device, which implies that transdermal interlocks suffer from many of the same limitations currently associated with breath-based interlocks. Improved methods for integrating alcohol and identification measurements are needed.
Spectroscopic measurements, such as those described by Robinson in U.S. Pat. No. 6,278,889 for glucose measurements, offer promise for completely noninvasive alcohol measurements in people. In U.S. Pat. No. 5,743,349, titled “Non-invasive optical blood alcohol concentration reader and vehicle ignition interlock system and method”, filed Sep. 23, 1996, since abandoned, Steinberg discloses a vehicle ignition interlock that incorporates a spectroscopic means for noninvasively measuring blood alcohol concentration. Steinberg does not disclose any means for verifying that the spectroscopic measurement is acquired from the prospective driver.
Furthermore, Steinberg discloses the measurement of electromagnetic radiation in the 250 to 3000 nm wavelength range by introducing radiation to a finger and measuring the light exiting the opposite side of the finger. Such transmission approaches, while potentially feasible in the visible region (400 to 800 nm), are limited by the strong absorption of water (water is a major component of the tissue) in the near and mid-infrared regions (>800). For tissue samples greater than a few millimeters in thickness, the absorption of water results in virtually no measurable radiation exiting the opposite side of the sample. Consequently, little if any radiation remains for subsequent measurement of alcohol concentration.
In U.S. Pat. No. 6,229,908, titled “Driver Alcohol Ignition Interlock”, filed Apr. 22, 1997, Edmonds and Hopta disclose an ignition interlock incorporating a spectroscopic alcohol measurement of the finger combined with a means for generating a finger print image. The finger print image is intended to identify the operator in order to ensure that the alcohol measurement was acquired from the prospective driver and not a passenger. Similar to existing breath-based interlocks, the finger print image is obtained from a measurement that is distinct from the spectroscopic measurement, thereby yielding potential for circumventing the interlock.